It is known to use polyphosphoric acid to ring-close diaryloterephthalic acids and to condition 2,9-difluoro-quinacridone and perylene (hydrazine) pigment and in connection with these prior art teachings, attention is directed to DOS No. 23 05 266, U.S. Pat. No. 28 21 530; DOS No. 21 48 866; DOS No. 20 58 577 and French No. 720207. However, conditioning with polyphosphoric acid is not known for the several classes of pigments enumerated below.